1. Field of the Invention
The present invention relates generally to RF subsystems for mobile and portable devices such as portable Global Navigation Satellite System (GNSS) receivers, 3G and 4G personal handheld devices and tablets, and portable WiFi and WiMax devices. GPS receivers are a part of GNSS receivers. More specifically, the present invention relates to unique approaches of distributed transmission/reception apertures that address two key concerns of RF antennas for portable and mobile devices: (1) fitting antennas into the limited space of a handheld device, while (2) maintaining the integrity of broad angular coverage. The same concepts can be extended for the hubs in microcells or those of Wifi and WiMax. Some potential advantages of the present invention include improved flexibility and utility efficiency of existing frequency assets.
2. Description of Related Art
Terrestrial wireless communication demands have experienced a massive increase in the last few decades due to the advent of WiFi, WiMax, 3G/4G networks, primarily due to the proliferation of portable hand-held devices that utilize such wireless communications technologies, such as 3G/4G cellular phones, tablet computers, portable music players, etc. This substantial increase in use of these devices has also resulted in a proliferation of IP-based products using ever-increasingly fast fiber optics and satellites for back-bone or transport applications. On the other hand, these high-speed access communications avenues to handheld devices are typically being emanated from ever-increasingly small wireless antennas. These small wireless antennas are required to radiate and receive in broad beams with near omni-directional capabilities, while maintaining suitable gain levels and power efficiencies despite receiving constant reductions in physical size. Therefore, effective spectrum utilization becomes more and more important due to the expeditious increase in demand for wireless “access” communications.
Currently, there are two key issues associated with these commercial wireless portable devices. Firstly, as the market for 3G and 4G portables continues to expand, demands for higher data rate channels continues to expand as well. With mobile frequency spectra becoming increasingly crowded, bandwidth becomes insufficient to satisfy current demand. Secondly, as a user holding a wireless hand-held device, its radiation/reception patterns or characteristics may change significantly due to interaction of the device and the user, either intentionally or unintentionally.
Presently, the majority of these wireless communications devices also have a navigational aids baked into the devices as well. It is therefore also desirable to explore antenna geometries that relate to Global Navigation Satellite Systems (GNSS). Specifically, it is desirable to explore antenna geometries that provide nearly full hemispherical coverage, in lieu of omni-directional antennas for data communications purposes. Key parameters of the 4 principle systems are listed in Table 1.
The United States NAVSTAR Global Positioning System (GPS) is currently the only fully operational GNSS. The Russian GLONASS is a GNSS in the process of being restored to full operation (it is practically restored, with 21 of 24 satellites operational by April 2010). On the other hand, the European Union's Galileo positioning system is a next generation GNSS in the initial deployment phase, with the In-Orbit-Validation (10V) phase taking place in 2010. Full Orbit Constellation (FOC) should be reached in 2015 (but this schedule is very flexible). China is also building up a global system called COMPASS, referred to as Beidou-2. Beidou-1 is a regional augmentation system.
TABLE 1Key orbital parameters of the 4 GNSS systems.GPSGLONASSGALILEOCOMPASSNumber of Satellites21 + 321 + 327 + 330 + 5 GEONumber of orbital planes633?Semi-major axis26600km25440km29600km? 21500kmOrbital revolution period11:58H11:15H14:07H? 12:35HInclination55deg64deg56deg? 55degSatellite Mass1100kg (IIR)1400kg700kg? 2200kgSolar panel area14m223m213m2???
This invention therefore intends to solve both issues in economical and efficient ways.
The distributed apertures may be configured to achieve broad beam width with a specified user holding the device. The distributed apertures may also be re-configured to form multiple orthogonal beams in order to enhance throughput for the portable devices. In particular, the applications of multiple small elements to “synthesize” radiation and receiving directional patterns dynamically for terrestrial wireless communications offer many potential advantages, including improved flexibility and utility efficiency of existing frequency assets.
Due to the technological advances concerning GPS/inertial navigation systems, low cost, mass-production hand-held GPS systems have become commonplace, such as those that use commercial off-the-shelf Micro-Electro-Mechanical System (MEMS) accelerometers and gyroscopes. It has become very practical to estimate the “orientations” and motion trends of individual personal portable devices with respect to a fixed coordination system. The MEMS inertial measurement unit (IMU) is packaged in a small size and provides the raw IMU data through a serial interface to a processor board where the inertial navigation solution and integrated GPS/inertial Kalman filter is generated. Thus, spatial diversity for better spectrum utility can be implemented by low-cost and reliable processing techniques for consumer wireless communications markets such as receiving handheld devices for navigation, 3G and 4G mobile devices, as well as WiFi and WiMax devices.